Companies typically maintain private enterprise networks, e.g. a private branch exchange (PBX), for providing a voice communication system within their premises. A subscriber can then establish a PBX call connection with another subscriber within the same PBX system without ever using a public carrier network, e.g. a Public Switched Telephone Network (PSTN) and/or a Public Land Mobile Network (PLMN). Since no PSTN or PLMN service is used in establishing the PBX call connection, no service charges would be levied against the PBX user by the public service provider. In the same way, many companies operate other forms of private enterprise networks, e.g. local area networks (LANs) for providing independent data communication systems. Such LAN communication enables multiple users to communicate and access Internet, e-mail and database servers.
Both in private enterprise networks and in public carrier networks, various call forwarding services are currently available. For instance, calls from a selected set of numbers can be forwarded to a number of the subscriber's choice. Other services automatically forward calls to another number when the subscriber's line is busy.
US 2004/100575A2 describes a method and system for call forwarding in a telephony network. A subscriber of the telephony network specifies caller groups which are stored as subscriber data in a home location register (HLR). When the subscriber connects to a mobile switching center (MSC), the subscriber data in a visiting location register (VLR) associated with the MSC is updated with the sub-scriber data in the HLR. A call originating from a caller in a nominated caller group is connected directly to the subscriber or the subscriber is notified of the incoming call. Connecting such a call to the subscriber may include disconnecting a pre-existing call.
US 2005/0096029 describes a method of forwarding calls for a subscriber having a primary communication device and a plurality of alternate communication devices in a multimedia telecommunication network. The method comprises storing a call forwarding-profile for the subscriber's primary communication device at a network sever. The call forwarding-profile specifies at least one of the alternate communication devices to which calls are to be forwarded, depending on whether they include voice, video or data media, for example.
US 2003/0069030 describes a system, a method and an apparatus for providing a subscriber feature supported by a private enterprise network to a mobile subscriber travelling within a public carrier network. Outgoing call connection requests by the subscriber are forwarded over the private enterprise network, even if the subscriber is roaming in the public carrier network. Such subscriber features include speed dialing, short dialing, corporate long distance services, conference calls, etc.
US 2001/0048738 describes a method and system for providing call forwarding in an IP telephone network based on call forwarding-profiles. The call forwarding is based on the type of callers, and one or more destination addresses can be specified. The call is connected to a first phone, if an active call forwarding-profile is not found. If an active call forwarding-profile is found, the call is routed to at least a third telephone based on the call forwarding-profile. The method and system described in US 2001/0048738 are limited to a single IP telephone network.
EP2048863 A1 describes a telecommunication system which routes an inbound telephone communication through an enterprise communication network. The communication is routed to a first user, and if the first user does not answer, the communication is routed to a second user, based on predetermined user profile information. Communications requests can only be forwarded to a user, if the user is connected to the enterprise communication network.